Single chip radio receiver with one off-chip filter

• US 5,031,233 A
• Filed: 07/11/1989
• Issued: 07/09/1991
• Est. Priority Date: 07/11/1989
• Status: Expired due to Term

• Current Assignee: Protocol-ip.com, LLC, Seiko Instruments Incorporated (Seiko Group)
• Original Assignee: AT&T, Inc.
• Inventors: Ragan, Lawrence H.
• Primary Examiner(s): Kuntz, Curtis
• Application Number:
  US07/378,724
• Time in Patent Office: 728 Days
• Field of Search: 455/182, 455/183, 455/192, 455/228, 455/231, 455/254, 455/307, 455/197, 455/344, 455/345, 455/338, 455/340, 333/24.1, 333/24 R, 333/1.1, 333/215, 340/825.44
• US Class Current: 455/307
• CPC Class Codes: H04B 1/1638 Special circuits to enhance selectivity of receivers not otherwise provided for resonant circuits H03H
• CPC Class Codes: H04W 52/0274 by switching on or off the equipment or parts thereof
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

The present invention provides an improved single chip radio receiver which has less external components than do previous similar receivers. With the present invention the integrated circuit which includes the radio receiver also has an on-chip adaptive filter. The radio receiver is designed for use in a radio pager which is only active for a very short time slot during a relative long repeat cycle. Thus the adaptive filter only need remain stable for a short period after its coefficients are adjusted to the desired values. The radio receiver includes an external filter which has the same frequency response as desired from the adaptive filter. Immediately prior to activating the radio receiver, the circuit is activated to adjust the parameters of the adaptive filter so that the adaptive filter matches the external filter. The radio receiver is then activated using both filters in series thereby producing the desired radio reception. The adaptive filter quickly changes characteristics; however, since the radio receiver is only active for a short period of time, operation of the system is not affected.

Claims

1. A single chip radio receiver designed for use in a radio pager said radio receiver having first and second filters which operate within a set of specifications to form an IF filter, said radio pager only being active for a very short time slot during a relative long repeat cycle, comprising,

an integrated circuit chip having radio receiver components thereon, including components connected to form said first filter which comprises capacitors and gyrators,

an external off-chip filter connected to form said second filter,

means for adjusting said on-chip filter to match said off-chip filter when said receiver is not operating,

means for connecting said on-chip and said off-chip filters together as said IF filter,

whereby said receiver can operate for a short period of time before said on-chip components drift out of said specification.

6. The radio receiver recited in claim 1 wherein said receiver is an FM receiver.

8. The receiver recited in claim 1 wherein said time slot is less than 40 milliseconds long, and wherein said on-chip filter is substantially matched to said external filter during each active period of said receiver.

2. A method of operating an integrated circuit radio receiver having an on-chip adaptive filter and a discrete filter, the method comprising the steps of:

connecting the adaptive filter and the discrete filter to a tuning circuit,

tuning the adaptive to form a tuned filter which emulates said discrete filter,

reconnecting the discrete filter and said tuned filter adaptive filter in the radio receiver circuit,

activating said radio receiver for a period shorter than the stable time period of said adaptive filter,

deactivating said radio receiver,

whereby during the active period of said receiver, said adaptive filter and said discrete filter operate in similar fashion.

3. The radio receiver in claim 2 wherein said adaptive filter includes a gyrator.

7. The method recited in claim 2 wherein said radio receiver is an FM receiver.

4. A radio receiver on an integrated chip said receiver including first on-chip IF filter and a second external IF filter said receiver including;

means for activating said receiver intermittently, each active period being relatively short,

on-chip components forming said first on-chip IF filter,

external components forming said second external IF filter,

means for adjusting said on-chip IF filter to match said external IF filter prior to each active period of said receiver, whereby said on-chip filter can maintain said setting for said short period of time said receiver is active.

5. The radio receiver recited in claim 4 wherein said radio receiver is an FM receiver.